(1) Field of the Invention
The present invention relates to a method and apparatus for generation of a high frequency pulse and for excitation of nuclear magnetic resonance of a sample and, in particular, relates to the above method and apparatus suitable for nuclear magnetic resonance imaging and nuclear magnetic resonance analysis.
(2) Prior Art
In the nuclear magnetic resonance imaging and the nuclear magnetic resonance analysis, a high frequency pulse is typically applied to the sample for excitation of nuclear magnetic resonance of the sample.
According to the well known technique, a high frequency or radio frequency wave (carrier wave) having a predetermined frequency is modulated with a modulation wave defined by a sinc function both ends of which are restricted in order to have a time width T and thereby while centering the above frequency, a high frequency pulse is generated which provides a frequency spectrum having a frequency band inversely proportional to the time width T.
However, since the time width of the modulation wave and the frequency band of the frequency spectrum are inversely proportional to each other, it was difficult to simultaneously satisfy both shortening of the time width of the modulation wave and hence the high frequency pulse width (which indicates radiation time on the sample with the high frequency pulse) and narrowing the frequency band.